TABLE.
Prevalence (per 10,000 live births) and estimated average annual number of spina bifida and anencephaly cases, by period and prenatal ascertainment status — 19 population-based birth defects surveillance programs, United States, 1995–1996 and 1999–2011*
| Type of case/Prenatal ascertainment status | Pre-fortification | Post-fortification | Difference in estimated annual cases between pre- and post-fortification | ||||||
|---|---|---|---|---|---|---|---|---|---|
|
|
|
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| 1995–1996 | 1999–2000 | 2001–1002 | 2003–2004 | 2005–2006 | 2007–2008 | 2009–2011 | 1999–2011 | ||
| Anencephaly | |||||||||
| Programs with prenatal ascertainment† | |||||||||
| Prevalence | 4.2 | 3.3 | 3.2 | 2.7 | 2.9 | 2.9 | 2.8 | 2.9 | |
| Estimated annual cases (95% CI) | 1,628 (1,440 –1,816) | 1,305 (1,139–1,471) | 1,277 (1,113–1441) | 1,105 (950–1,260) | 1,222 (1,059–1,384) | 1,231 (1,067–1,394) | 1,127 (1,000–1,255) | 1,206 (1,142–1,269) | 422 (298–547) |
| Programs without prenatal ascertainment§ | |||||||||
| Prevalence | 2.3 | 2.3 | 1.9 | 1.9 | 1.7 | 1.8 | 1.9 | 1.9 | |
| Estimated annual cases (95% CI) | 913 (827–1,000) | 924 (847–1,001) | 774 (704–845) | 778 (708–849) | 701 (634–768) | 763 (693–833) | 760 (703–817) | 781 (754–809) | |
| Spina bifida | |||||||||
| Programs with prenatal ascertainment† | |||||||||
| Prevalence | 6.5 | 4.0 | 4.5 | 3.7 | 4.0 | 4.4 | 3.7 | 4.0 | |
| Estimated annual cases (95% CI) | 2,549 (2,314–2,785) | 1,617 (1,433–1,802) | 1,792 (1,598–1,986) | 1,517 (1,336–1,698) | 1,678 (1,487–1,868) | 1,869 (1,668–2,070) | 1,476 (1,330–1,622) | 1,645 (1,571–1,719) | 904 (743–1,066) |
| Programs without prenatal ascertainment§ | |||||||||
| Prevalence | 4.3 | 3.5 | 3.3 | 3.5 | 3.2 | 3.4 | 3.6 | 3.4 | |
| Estimated annual cases (95% CI) | 1,685 (1,568–1,803) | 1,405 (1,310–1,501) | 1,326 (1,234–1,418) | 1,426 (1,330–1,521) | 1,328 (1,236–1,420) | 1,455 (1,359–1,551) | 1,443 (1,365–1,521) | 1,401 (1,364–1,438) | |
| Anencephaly and spina bifida | |||||||||
| Programs with prenatal ascertainment† | |||||||||
| Prevalence | 10.7 | 7.3 | 7.6 | 6.4 | 6.9 | 7.2 | 6.5 | 7.0 | |
| Estimated annual cases (95% CI) | 4,177 (3,876–4,479) | 2,922 (2,674–3,170) | 3,069 (2,815–3,323) | 2,622 (2,384–2,860) | 2,899 (2,649–3,150) | 3,100 (2,840–3,359) | 2,604 (2,410–2,797) | 2,851 (2,754–2,948) | 1,326 (1,122–1,531) |
| Programs without prenatal ascertainment§ | |||||||||
| Prevalence | 6.7 | 5.8 | 5.2 | 5.4 | 4.8 | 5.2 | 5.5 | 5.3 | |
| Estimated annual cases (95% CI) | 2,599 (2,453–2,745) | 2,329 (2,206–2,452) | 2,100 (1,984–2,216) | 2,204 (2,085–2,322) | 2,029 (1,915–2,143) | 2,218 (2,100–2,337) | 2,203 (2,107–2,299) | 2,182 (2,136–2,228) | |
| Average annual live births ¶ | 3,895,542 | 4,009,116 | 4,023,830 | 4,101,001 | 4,201,952 | 4,281,964 | 4,027,880 | 4,101,490 | |
Abbreviation: CI = confidence interval.
Estimated annual number of cases for the specified period is calculated by multiplying the prevalence by the average number of U.S. annual live births. Data during the optional fortification period (1997–1998) are not presented.
States with prenatal ascertainment (n = 8): Arkansas, Georgia, Iowa, New York, Oklahoma, Puerto Rico, South Carolina, and Utah.
States without prenatal ascertainment (n = 11): Arizona, California, Colorado, Illinois, Kentucky, Maryland, New Jersey, North Carolina, Texas, West Virginia, and Wisconsin.
Data available at http://wonder.cdc.gov.